Hone Harawira has congratulated Te Tai Tokerau MP Kelvin Davis on being appointed deputy leader of the Labour Party.

"This is a special day for Kelvin and his whānau and for Te Tai Tokerau," the former electorate MP says. "He deserves my congratulations. Not many of us get even close to the leadership of a political party."

"He'll have many challenges in the coming days... no doubt many will come from me, but on this day, I wish him the best.

When Newshub asked Mr Harawira if it's "game on" from tomorrow, he replied: "Call me back at one minute past midnight."

2:45pm: ACT leader takes aim at Labour leader's age

ACT leader David Seymour has questioned Jacinda Ardern's credibility because of her age.

"I don't think it's credible to have a 39-year-old Prime Minister in coalition with Metiria Turei and Winston Peters," 34-year-old Mr Seymour says about Ms Ardern, who is actually 37.

Green co-leader Metiria Turei says she has "really enjoyed working with Andrew Little over the past years.

"He's a man with great integrity and I'm sad that he's no longer the leader.

"But I've also worked with Jacinda Ardern over a number of years in Parliament, I hold her in very high regard and I'm very pleased that she has this new role as leader and I'm looking forward to working with her to change the Government in September."

The ACT party have accidentally called Jacinda Ardern the "new PM" in a since-deleted post on Twitter.

Photo credit: Twitter / ACT Party

They've since corrected their mistake in a second tweet.

2:15pm: Bill English predicts challenges for Jacinda Ardern

Prime Minister Bill English has predicted Jacinda Ardern will face some of the same problems former leader Andrew Little faced.

"I'm sure she's a competent politician," he says. "The real problem for her is the Labour Party and their lack of progress over nine years and in the end that's what put the pressure on Andrew Little.

"The contest of ideas is going to matter more than particular personalities.

"I think she's got some real challenges particularly with the lack of momentum and ideas within the Labour party."

Nikki Kaye, who has battled with Ms Ardern in the past over the Auckland Central seat, has congratulated the new Labour leader.

"I've actually just sent a message to her congratulating her," she says.

2:06pm: Jacinda Ardern's first appearance in parliament as Labour leader

Jacinda Arden wasted little time in Parliament on Tuesday, asking the first question of the day as leader of the opposition to Prime Minister Bill English.

"Sir speaker, my question is to the Prime Minister: Does he stand by his statement on the housing crisis that quote 'I wouldn't call it a crisis, we have strong demand, we have an uplift in prices, these are good problems to have, actually' end quote."

"First of all can I congratulate the member on her new role as leader of the opposition," he replied. "Mr Speaker I stand by my full statement on emergency housing…"

1:35pm: Hundreds of Andrew Little billboards to change

Hundreds of Labour Party billboards that were put up by volunteers around the country only last week will need to be replaced.

The hoardings, erected across 71 electorates, were hammered into the ground by students and other members of the public.

With only seven weeks until the election, Labour Party general secretary Andrew Kirton says there's a lot of work to do replacing Andrew Little with Jacinda Ardern and Kelvin Davis.

"We got a lot of people in Labour that can swing a hammer very well and very effectively. My old man was up putting them up in Taumaranui the other day. When the call goes out I know our party will come forward."

"It'll be a fair few days, there's 71 electorates, New Zealand's quite long and thin so we'll take stock of that and we'll decide how we go forward with it."

Television ads, online ads, and pamphlets will also need to change - meaning a costly campaign for Labour.

"We're going to work through all of those issues, we've got the money to do it, we're running at 300 percent higher campaign income this time than 2014, we've got the money - I think some more will come in now - and we'll get cracking and do it" Mr Kirton says.

"You know what? I'm quite relaxed about it because it's one of those things that we've just got to work through and we'll get stuck in and get it done.

"There's always the unexpected, this is unexpected for sure but we're really excited now, we got a campaign of our lives ahead of us now and it's just about getting down there, head down, bum up, and cracking through it.

"The clock is ticking and we know that and we got the campaign of our lives ahead of us."

Twitter users have started to come up with a campaign idea of their own:

12.58pm - The fight for the north

The Labour Party's constitution puts the deputy leader at number two.

Kelvin Davis was previously not on the list at all, instead counting on a win in Te Tai Tokerau to make it back into Parliament in September.

Last election Mr Davis won the seat off Hone Harawira by a margin of 743 votes. But at the time, Mr Harawira had been burned in the north by the shortlived Internet-MANA alliance.

This time, Mr Harawira has formed an alliance with the Māori Party, who will allow him a clear run as part of an attempt to unseat Labour in the north.

Mr Harawira is likely to be pleased the heat is off the voters of Te Tai Tokerau. Now they can vote for Mr Hawawira and bank on getting Mr Davis representing them in Parliament too.

12pm - Jacinda Ardern to speak for the first time as Labour Leader

Ms Ardern is addressing the nation as leader of the Opposition for the first time.

Mr Little's "announcement today... is not what anyone expected or wanted," she said.

"We are determined and steadfast and I consider myself incredibly lucky to now call myself leader."

"These are extraordinary circumstances. I have been asked to take on this challenge. I have accepted. I'm confident I can lead this team into the election."

Addressing concerns about her age, Ms Ardern said, "Granted I am a young proposition for the party, but this party has worked alongside me for nine years, they have faith in me, and I'm for the job."

Ms Ardern said Mr Davis is "an exceptional member of Parliament and also an exceptional member of his community."

When asked whether she could pull together a Government with NZ First and the Greens, Ms Arden quipped: "I used to be the President of an international youth organisation that had members from Lebanon, Palestine and Israel. I think I can do this."

Ms Ardern said she hasn't even had a chance to share the news with her parents.

Jacinda Ardern addresses the media for the first time as leader of the Opposition.
Photo credit: Lloyd Burr/Newshub.

11.45am - Māori Party to Labour: Work with us for our people's sake

Māori Party president Tukoroirangi Morgan has called on the Labour Party to work with them "in the best interests of Aotearoa."

"Māori people throughout the country are telling me they want our party to work with Labour if it's in a position to form a Government after September 23," Mr Morgan said.

"We're hoping Jacinda and Kelvin won't be as closed minded and that they’ll agree to work with kaupapa Māori.

"Like Labour our party is concerned about more than half the prison population being Māori, not enough Māori people owning their own homes, whānau ora not getting enough funding to make the difference we want it to and the shocking number of people sleeping in their cars and on the streets."

But do the numbers stack up?

On Newshub's current polling, Labour needs the Greens and NZ First to form a Government.

The Māori Party are unlikely to work with NZ First, as Winston Peters wants a referendum on abolishing Māori seats.

According to our back-of-the-envelope calculations, the Māori Party does not bring enough MPs for Labour to form a Government without NZ First.

11.28am - Ardern thanks Little

Jacinda Ardern has tweeted her thanks to Mr Little

"I want to thank Andrew - for his huge work and his leadership, and giving me the chance to work alongside him," she said.

"I feel privileged and honoured to have been elected leader of the Labour Party, and ready for the challenge! Bring on 23 September."

11.18am - Who is Kelvin Davis?

Mr Davis is the MP for Te Tai Tokerau and the party spokesperson for Corrections, Māori Development and Treaty of Waitangi Negotiations. He's a former teacher and Northland school principal and was elected to Parliament in 2008.

He's also now deptuy leader of the New Zealand Labour Party.

Labour's Kelvin Davis.
Photo credit: Simon Wong/Newshub.

11am - Commentators, politicians respond

Reporters at RadioLIVE have compiled responses to Mr Little's resignation from commentators, reporters and politicians.

James Shaw, Green Party co-leader: "I think that given their polling results… a radical move was called for, so I’m not hugely surprised."

Carmel Sepuloni, Labour Party: "Andrew’s done a great job for us, and we admire the fact that’s he's made this decision to step aside. But at the same time, you feel of two minds. Of course there is a little bit of sadness, but we've got to get on with the job, and that's winning the election."

Lloyd Burr, Newshub reporter: "I don’t know if Jacinda Ardern and Kelvin Davis – if they go in on this together – if they are going to boost the polling enough to govern. They are probably looking long-term now. They've probably written this election off."

Chris Trotter, political commentator: Says Jacinda Arden's unwillingness to take up the leadership makes her the best person for the job.

“In this particular Labour caucus, any sign of naked ambition is pretty much the equivalent of attaching a very large target to your back.”

10.36am - Labour deciding on new leader

Labour's Caucus members are currently meeting to decide on their new leader.

Mr Little said they will emerge from the meeting with a decision made on the new Labour Party leader this morning.

If Jacinda Ardern emerges from the meeting as leader of the Labour Party, she will have to go face-to-face against Prime Minister Bill English for Question Time in the House today at 2pm.

10am - Mr Little announces resignation

Mr Little has stepped down as Labour leader.

In a press conference, he told media poll results were "disturbing" and "very very disappointing".

"It became pretty clear that the story around those polls was building a narrative... I take responsibility for that," he said.

"It is my judgement that the party and the people we are campaigning for will be better served by a new leader that can bring a fresh face and a fresh voice.

"The campaign we will need to run over the next seven and half weeks will be tough. We will have to be determined, it will be a big fight," he said.

He said he expects Jacinda will be nominated or step up. Little said Ardern will have his full support.

Mr Little said it was his own choice to step down.

Mr Little's statement of resignation:

"Today I have announced that I will step down as leader of the Labour Party.

I’m proud to have been leader of the Labour Party, and have given this position my absolute and unwavering dedication, just as I have done so for more than 25 years in the Labour movement.

While obviously this is a sad decision, I have been privileged to have led a united, talented team of Labour MPs, proud to have progressed the values and issues that New Zealanders care about and proud to stand with working New Zealanders.

I remain committed to the Labour cause of putting people first, lifting the rights of working New Zealanders and strengthening Kiwi families.

The Labour team of MPs and staff have worked incredibly hard during my leadership, however recent poll results have been disappointing.

As leader, I must take responsibility for these results. I do take responsibility and believe that Labour must have an opportunity to perform better under new leadership through to the election.

I am determined to make sure that Labour fights this campaign with the greatest of resolve, because far too much is at stake for far too many New Zealanders.

New Zealand needs a Labour-led Government, and in order to achieve this Labour must fight without questions over its leadership.

The campaign is on a good footing, Labour’s caucus is united and the party is healthy.

My colleagues in the Labour Party caucus will elect a new leadership team this morning. I wish my successor all the very best in their new role, and offer my wholehearted support to them."

9.40am - Phil Twyford rules out running for leader

Phil Twyford will not say whether he would support Andrew Little in a vote of no confidence today.

Mr Twyford ruled out running for leadership himself.

9.21am – Who can pass a vote of no confidence in the leader?

If Mr Little does not step down as leader, that leaves it up to Labour’s Caucus to call a vote of no confidence themselves.

In order for a leadership election to be called, at least 50 percent plus one member of Caucus must say they do not endorse the leader, according to Labour’s 2016 constitution.

Because it’s fewer than 100 days out from an election, Caucus can vote in a new leader without the process going out to membership and unions for a wider vote.

The leader must have support from at least 60 percent plus one member of Caucus.

9.07am - Ardern says she supports Little

When asked by Newshub's Jenna Lynch whether she would run against Mr Little, Ms Ardern did not rule it out.

"Andrew's had my support the entire time," Ms Ardern said.

8.50am - 'F**k it I'm going to fight'

Political commentator Bryce Edwards says a Labour Party insider told him "Andrew Little has changed his mind about stepping down and has said "F**k it, I’m going to fight".

"A Labour insider tells me that Andrew Little has changed his mind about stepping down and has said “F**k it, I’m going to fight”.
Photo credit: Bryce Edwards/Twitter

8.38am - Little says he's not resigning

Andrew Little has told an RNZ reporter at Wellington airport he will not resign as leader at Labour's Caucus meeting today.

8.23am - Phil Twyford for Labour Leader?

Patrick Gower reports there is discussion within the Labour Party of Phil Twyford possibly stepping in as leader.

Gower says there is also talk of a Jacinda Ardern-Kelvin Davis combination.

Labour MPs - who's backing who?

The Newshub politics team has asked a number of Labour Party politicians where their support lies.

Peeni Henare wouldn't say whether Little has his support.

David Parker said he would "always support the leader" but wouldn't utter the words 'Andrew Little'.

Clare Curran offered no comment.

Stuart Nash said he has "no idea what's happening today."

Adrian Rurawhe, MP for Te Tai Hauāuru, said Mr Little has his support.

Jacinda Ardern did not rule out running against Mr Little but said he has always had her support.

Mike Williams, former president of the New Zealand Labour Party, told Newshub he expects Mr Little to resign and Ms Ardern to replace him as leader of the party, with Kelvin Davis as her deputy.

Mr Williams said Labour needs a 'circuit breaker'.

7.36am - The Greens would work with Little or Ardern, hint at support for Little

Green Party co-leader Metiria Turei told The AM Show she could work with either Ms Ardern or Mr Little, but she said persistence pays off in politics.

"I've learnt from Winston Peters quite a bit about politics and one of those things is persistence; that this is a game of nerve. You have to be persistent and strong. That's what leadership looks like in politics."

Ms Turei said her own party has been rewarded in the polls for taking a risk on policy, a reference to a swell in support after her much-publicised admission of benefit fraud. The confession was part of a policy release that would see benefit levels rise and many sanctions removed.

"I have been delivering that leadership for the Green Party. That’s why we have been so strong on ending poverty and prepared to take risks with our policy to communicate that to New Zealanders. And that call out has meant New Zealanders are looking to the Greens for leadership," she said.

Metiria Turei on The AM Show.
Photo credit: Newshub.

7am - Māori Party open to negotiation with new Labour leadership

Māori Party co-leader Marama Fox speculated a new Labour leadership could potentially work with the Māori Party.

"Would the new line up work with us? Little said he wouldn't - maybe a new line up will see sense #MaoriAtTheTableAlways," she tweeted.

6.30am - Expect to see a new Labour leader this morning: Gower

"[Andrew Little] has to make up his mind whether he goes into that Caucus and faces this potential vote of no confidence," Newshub political editor Patrick Gower told The AM Show.

"Or his alternative option is to go into that Caucus and resign as leader.

"I expect we see a new leader of the Labour Party later on this morning. I would say it would be Jacinda Ardern," he said.